Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables)
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9 Months Ended |
Sep. 30, 2021 |
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| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
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| Summary of Option Activity |
The following table summarizes option activity under the Company’s 2004 Plan, 2018 Plan and 2021 Plan:
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Shares
|
|
|
Weighted-
Average
Exercise Price
|
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Weighted-
Average
Remaining
Contract Term
(Years)
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Aggregate
Intrinsic Value
(in thousands)
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Stock options outstanding at December 31, 2020
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5,439,295
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$
|
11.93
|
|
|
|
7.75
|
|
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$
|
53,202
|
|
|
Granted
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1,383,950
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|
$
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20.40
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|
|
|
|
|
|
|
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Exercised
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(185,974
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)
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$
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10.60
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|
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|
|
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Canceled and forfeited
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(103,499
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)
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$
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10.58
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|
|
|
|
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Stock options outstanding at September 30, 2021
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6,533,772
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$
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13.78
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|
|
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7.65
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$
|
35,715
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|
|
Stock options exercisable at September 30, 2021
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3,523,838
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$
|
12.73
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6.80
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$
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21,959
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| Schedule of Employee Stock Options Valuation |
For determining stock-based compensation expense, the fair-value-based measurement of each employee stock option was estimated as of the date of grant using the Black-Scholes option-pricing model with assumptions as follows:
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Nine Months Ended
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|
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September 30,
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|
|
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2021
|
|
|
2020
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Expected term (in years)
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|
5.3-6.1
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|
|
5.1-7.0
|
|
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Expected volatility
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81.6%-84.9%
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73.2%-84.2%
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Risk-free interest rate
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0.6%-1.1%
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0.2%-1.6%
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Expected dividend
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–
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–
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| Summary of Status and Activity of Non-vested RSUs |
A summary of the status and activity of non-vested RSUs during the nine months ended September 30, 2021 is as follows:
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Number of
shares
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|
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Weighted
Average
Grant-Date
Fair Value
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Non-vested December 31, 2020
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666,375
|
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$
|
9.83
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Granted
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1,913,750
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$
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20.56
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Vested and released
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(232,474
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)
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$
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11.06
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Canceled and forfeited
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(84,875
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)
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$
|
17.07
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Non-vested September 30, 2021
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2,262,776
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$
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18.50
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|
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| Schedule of Fair Value of ESPP Shares Using Option Pricing Model |
For the nine months ended September 30, 2021 and 2020, the fair value of ESPP shares was estimated using the following assumptions:
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Nine Months Ended
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September 30,
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2021
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|
|
2020
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|
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Expected term (in years)
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0.5
|
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0.5
|
|
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Expected volatility
|
65.9-111.4%
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|
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94.1
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%
|
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Risk-free interest rate
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0.1
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%
|
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0.4
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%
|
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Expected dividend
|
|
–
|
|
|
|
–
|
|
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| Schedule of Stock-Based Compensation Expense Recognized |
Total stock-based compensation expense recognized was as follows:
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Three Months Ended
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Nine Months Ended
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|
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|
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September 30,
|
|
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September 30,
|
|
|
|
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2021
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|
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2020
|
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2021
|
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2020
|
|
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(in thousands)
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(in thousands)
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|
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Research and development expense:
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$
|
1,933
|
|
|
$
|
761
|
|
|
$
|
4,882
|
|
|
$
|
1,972
|
|
|
General and administrative expense:
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|
$
|
4,562
|
|
|
|
2,351
|
|
|
|
11,472
|
|
|
|
6,858
|
|
|
Total
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|
$
|
6,495
|
|
|
$
|
3,112
|
|
|
$
|
16,354
|
|
|
$
|
8,830
|
|
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| Summary of the Status of Call Options |
A summary of the status of the call options as of September 30, 2021 and December 31, 2020 is as follows:
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September 30,
|
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December 31,
|
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2021
|
|
|
2020
|
|
|
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Shares
|
|
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Shares
|
|
|
Options vested and exercised
|
|
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257,834
|
|
|
|
257,834
|
|
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Options vested and outstanding
|
|
|
4,445
|
|
|
|
-
|
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Options unvested and outstanding
|
|
|
4,445
|
|
|
|
8,890
|
|
|
Total options granted
|
|
|
266,724
|
|
|
|
266,724
|
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|